Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 222336
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
636 PM CDT Thu Oct 22 2020

.SHORT TERM...(This Evening through Friday)
Issued at 234 PM CDT Thu Oct 22 2020

Much of the heavier precipitation will be out of the area by early
evening, but some patchy drizzle and freezing drizzle will remain
possible along with some light to briefly moderate snow. The better
chances for snow will be west of I-29 in what should be a skinny
band of snow that moves through. This is in response to a strong
push of drier and colder air aloft moving in as the system exits.
The forcing along this front weakens after about 3z so not
anticipating too much accumulation. Maybe an inch or a little more
around Huron and Wessington Springs this afternoon then lesser
amounts farther east as the band weakens. Overall conditions will
gradually improve into the evening as winds weaken a touch and
precipitation diminishes.

Northerly flow is expected on Friday ahead of incoming high
pressure. This will bring a very chilly morning to the area on
Friday with wind chill values in the teens brought by northwest
winds of 15 to 25 mph. Clouds may be a bit stubborn to erode but
will definitely not be as thick as today. Even if we clear out the
diurnal range will be pretty small. Morning lows mostly mid to upper
20s with highs in the upper 20s to mid 30s. Not expecting
precipitation Friday or Friday night.

.LONG TERM...(Friday Night through Thursday)
Issued at 234 PM CDT Thu Oct 22 2020

Friday night into Saturday an upper level trough digs into the
Rockies as low pressure at the surface develops in CO. Latest models
appear to support a continued trend south. This does not mean we
will not get any snow, but a better chance to remain mostly light.
Do not expect any snowfall Friday night as flow in the lower levels
continues to support dry air advection from the east. By about late
Saturday morning the low levels begin to saturate in central SD and
this saturation gradually spreads across the area through the
afternoon into the evening. Saturday night into Sunday morning the
wave will eject onto the Plains and bring a better chance for
widespread snowfall. Overall this appears to be mainly a broad
isentropic lift event which usually supports a larger area of
snowfall, but avoids localized enhanced higher amounts like banded
events. The latest GFS does indicate a decent mid level band near
the Missouri River around 700-750mb, so will need to keep an eye on
the trends with that as a possible focus for some higher amounts.
Overall this system appears to be on par for about 2 to 4 inches in
many spots.

Once this system passes and drier air moves into the region on
Sunday night and will bring a couple of very cold, dry days. Sunday,
Monday and Tuesday will see highs roughly 25 to 35 with morning lows
in the single digits and teens.

The potential for a brief warm up but confidence pretty low on that.
Regardless the warm up would still not get us back to normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 636 PM CDT Thu Oct 22 2020

Primary aviation concern is ceilings through early tomorrow
afternoon. Light snow currently around KHON will slowly weaken and
shift northeast as the frontal band continues to weaken. Expect
MVFR visibilities 01Z before rising to 6 miles or higher the rest
of the night. There is a small chance of additional light snow
developing later tonight which could produce 3-5SM visibility
around KHON or KFSD but the probability is only 20-30 percent so
did not include in the TAF.

Otherwise, low clouds will be an issue into Friday. Expect clouds
to remain around 1000 ft through early tomorrow morning. As drier
air moves in and the surface slowly warms, ceilings should rise
to 2000 ft or higher by late morning. Ceilings are most likely to
rise over 3000 ft in the afternoon and skies may become SCT as
well. While less likely should temperatures remain colder, MVFR
ceilings could persist well into the afternoon.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 7 PM CDT this evening for
     SDZ038>040-052>067.

MN...Winter Weather Advisory until 10 PM CDT this evening for MNZ071-
     072-080-081-089-090-097-098.

IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...Schumacher



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